Internal combustion engines with a direct injection of fuel into the combustion chamber are generally known. A distinction is made between stratified charge or stratified operation as the first operating mode and homogeneous operation as the second operating mode. Stratified operation is used in particular at lower loads, while homogeneous operation is used at higher loads on the internal combustion engine. In stratified operation, fuel is injected into the combustion chamber, i.e., in the immediate vicinity of a spark plug, during the compression stroke. Therefore, there cannot be a uniform distribution of fuel in the combustion chamber. The advantage of stratified operation is that with a very small amount of fuel, lower loads can be handled by the internal combustion engine. However, greater loads cannot be handled by stratified operation. In homogeneous operation intended for such higher loads, fuel is injected during the intake stroke of the internal combustion engine, sc that fuel is swirled and thus easily distributed in the combustion chamber. To this extent, homogeneous operation corresponds approximately to an internal combustion engine operating mode where fuel is injected into the intake pipe in the traditional manner.
In both operating modes, i.e., in stratified operation and in homogeneous operation, the amount of fuel to be injected is controlled and/or regulated at an optimized level with regard to fuel injection, a reduction of emissions and the like by a control unit as a function of a plurality of parameters.
For starting such a conventional internal combustion engine with direct injection, it is known that an electric starter motor can be used to start the internal combustion engine, and then, after approximately one or two revolutions of the engine, fuel is injected into the combustion chambers and ignited according to the second operating mode, i.e., according to a homogeneous operation. With regard to starting-and-stopping operation of an internal combustion engine, e.g., when stopping at red lights and starting up again, the starting procedure described above is associated with unacceptably high fuel and electric power consumption.
An object of the present invention is to provide a method for starting an internal combustion engine with a lowest possible amount of electric power and/or fuel.